1. Field of the Invention
The present invention relates to light communication. More particularly, the present invention relates to an optical receiver for wireless light communication using light in the visible wavelength band.
2. Description of the Related Art
Conventional wireless light communication systems employ infrared wavelengths (i.e. IR communication systems), and their development has reached the level of Fast Infrared (FIR), with capacities of about 4 Mb/s (or more). Typical IR communication systems are commonly used purposes such as device control, as in the case of TV remote controls.
However, conventional IR communication systems have a problem in that the emission characteristics of IR rays require aiming the communication path of the devices for efficient communication, and that the invisibility of emitted light makes it difficult to determine the accuracy of the aim and perform any immediate reaction to adjust the position of a device.
In addition to IR communication, a visible light communication (VLC) system utilizing a white LED has recently been proposed, the installation and construction of which are disclosed in detail in Korean Laid-open Patent No. 10-2005-71617. The optical receiver of the proposed visible light communication system includes a lens, an optical filter, and a photoelectric transformation device (e.g. an optical detector or a phototransistor). The optical receiver detects data from light in the visible wavelength band, which has been applied to the system.
However, conventional optical receivers used for visible light communication systems have a problem in that because they employ visible light for communication, the wavelength band of which overlaps and has interference problems with many of the wavelength bands of light commonly encountered in daily life. In particular, such optical receivers in a VLC system are heavily affected by sunlight.
In other words, in a conventional VLC system, when the optical receivers receive light in the overlapping wavelength bands, which are not employed by their communication systems, erroneous operation or inaccurate data detection may occur. Furthermore, VLC communication systems may have to be used in a limited manner depending on the lighting of the environment.